Predicting laser beam propagation in a naval environment

Directed infrared countermeasure (DIRCM) systems are being developed in several configurations ranging from open loop, closed loop (CLIRCM) and lately for preemptive use (PIRCM). Critical performance parameters, from an atmospheric propagation point of view, include attenuation as well as turbulence effects on target detection, tracking and the capability to deliver enough power to the target (power in bucket). In order to evaluate the performance of DIRCM and other laser applications in a naval environment we have performed laser beam propagation studies over the Baltic Sea during June to October 2003. The experimental data were used to derive atmospheric attenuation, irradiance fluctuation parameters for different beam offsets relative to the beam centre, temporal and amplitude signal distributions, probability and mean time of fade and tracking performance. Results from simultaneous single and double-ended paths were obtained. This paper will shortly summarize the results from this campaign, and discuss and exemplify how the results can be used for prediction of DIRCM system performance.